What impact do glacial periods have on repository safety? This question was the subject of discussion among interested participants and experts on 20 June 2025 as part of the new digital BASE lecture series on research – scienceBASEd.

Climate fluctuations must be considered in the repository search process

Natural climate fluctuations have occurred since the beginning of Earth’s history. Ice ages can be divided into glacial (cold) and interglacial (warm) periods. The last glacial period ended around 11,000 years ago and left clear traces in the rock layers of Central and Northern Europe through widespread glaciation and permafrost. We are currently living in a warm period within the present ice age. The safety assessment period for a repository for high-level radioactive waste spans one million years. Over such a timeframe, it is expected that several ice ages with corresponding temperature fluctuations will occur. Therefore, potential effects of future glacial periods must be considered in safety assessments of the repository system. 

BASE has investigated this topic through two research projects: 

What effects do changing boundary conditions (e.g. due to future cold and warm periods) have on the development of the repository system? (AREHS research project) and Evaluation of methods and models for forecasting the protective function of the overburden (e.g. influenced by glacial erosion) in Germany over a period of 1,000,000 years (MeMoDeck research project).

Agenda

• 13:00 Welcome | Jochen Ahlswede (BASE)
• 13:15 Research project AREHS | Rene Kahnt (G.E.O.S Ingenieurgesellschaft mbH)
• 13:50 Research project MeMoDeck | Matthias Brandt (IfG Institut für Gebirgsmechanik GmbH)
• 14:20 Questions and discussion | Ingo Kock (BASE)
• 14:30 Conclusion | Esther Kähler (BASE)

Findings from the BASE research projects AREHS and MeMoDeck

The AREHS project used coupled numerical simulations to examine the effects of recurring ice ages on the geological subsurface. The results show that glacial cycles leave lasting imprints, such as changes in pressure conditions, stress states and temperature distributions. These temperature changes may result from the development of permafrost or the advance and retreat of glaciers. These “fingerprints” of past glaciations are still evident in measurement data today and shape the initial conditions for future modelling.

Since AREHS used generic (i.e. non-site-specific) models, the results could only be partially verified against real-world data. Nevertheless, the project provides valuable foundations for safety analyses in the repository site selection process. The automated workflow developed within the project allows for efficient application of these methods to specific sites in the future. In the MeMoDeck project, model simulations were also carried out, with a focus on the formation of glacial channels and how to manage associated uncertainties. Simulations for an abstract site with varying geological and hydrological conditions produced estimates for possible channel depths. These results will support BASE in further evaluations.

Takeaways from the event

Around 100 interested participants came together for the inaugural edition of the digital lecture series scienceBASEd to learn about and discuss the results of BASE research. Among them were interested members of the public, scientists and stakeholders involved in the site selection process. One key topic discussed was the extent to which the simulation results from the MeMoDeck research project are grounded in reality, as their direct applicability was not immediately apparent. The contractor responsible for MeMoDeck sees potential here for further simulations that could address this. The lecture, the ensuing discussion and the high level of interest shown in the event demonstrated that this form of scientific exchange is worthwhile for all involved. For questions or comments, further information, or if you are interested in the presentation slides, please contact: